全文获取类型
收费全文 | 13316篇 |
免费 | 293篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 195篇 |
综合类 | 17篇 |
化学工业 | 1938篇 |
金属工艺 | 273篇 |
机械仪表 | 308篇 |
建筑科学 | 495篇 |
矿业工程 | 23篇 |
能源动力 | 247篇 |
轻工业 | 1634篇 |
水利工程 | 111篇 |
石油天然气 | 30篇 |
无线电 | 1399篇 |
一般工业技术 | 1892篇 |
冶金工业 | 3183篇 |
原子能技术 | 172篇 |
自动化技术 | 1727篇 |
出版年
2022年 | 111篇 |
2021年 | 192篇 |
2020年 | 114篇 |
2019年 | 172篇 |
2018年 | 205篇 |
2017年 | 200篇 |
2016年 | 239篇 |
2015年 | 146篇 |
2014年 | 277篇 |
2013年 | 610篇 |
2012年 | 470篇 |
2011年 | 594篇 |
2010年 | 472篇 |
2009年 | 465篇 |
2008年 | 533篇 |
2007年 | 514篇 |
2006年 | 426篇 |
2005年 | 418篇 |
2004年 | 336篇 |
2003年 | 328篇 |
2002年 | 298篇 |
2001年 | 306篇 |
2000年 | 288篇 |
1999年 | 328篇 |
1998年 | 1014篇 |
1997年 | 630篇 |
1996年 | 476篇 |
1995年 | 352篇 |
1994年 | 286篇 |
1993年 | 300篇 |
1992年 | 163篇 |
1991年 | 145篇 |
1990年 | 152篇 |
1989年 | 151篇 |
1988年 | 143篇 |
1987年 | 111篇 |
1986年 | 122篇 |
1985年 | 158篇 |
1984年 | 115篇 |
1983年 | 97篇 |
1982年 | 84篇 |
1981年 | 99篇 |
1980年 | 95篇 |
1979年 | 96篇 |
1978年 | 52篇 |
1977年 | 114篇 |
1976年 | 162篇 |
1975年 | 54篇 |
1974年 | 43篇 |
1973年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We study the problem of learning parity functions that depend on at most k variables (k-parities) attribute-efficiently in the mistake-bound model. We design a simple, deterministic, polynomial-time algorithm for learning k-parities with mistake bound . This is the first polynomial-time algorithm to learn ω(1)-parities in the mistake-bound model with mistake bound o(n).Using the standard conversion techniques from the mistake-bound model to the PAC model, our algorithm can also be used for learning k-parities in the PAC model. In particular, this implies a slight improvement over the results of Klivans and Servedio (2004) [1] for learning k-parities in the PAC model.We also show that the time algorithm from Klivans and Servedio (2004) [1] that PAC-learns k-parities with sample complexity can be extended to the mistake-bound model. 相似文献
52.
简要叙述ISI、i-safe和IBI 3种典型的本质安全评价方法,说明其含有的参数及指数的计算方法;然后使用这3种方法评价了直接氯化法、氧氯化法、改进的氧氯化法3个EDC生产流程.评价结果表明:不同方法评价相同的几个过程,得到的各过程安全性的高低是一致的:直接氯化法最高、氧氯化法次之、改进的氧氯化法安全性最差:评价同一个流程时,ISI法评价得到的数值最大,i-Safe法次之,IBI法最小.结合评价的过程从参数的个数及覆盖面的大小、参数取值的主观性程度、获取所需信息的难易程度和结果的灵敏性4方面比较和分析3种评价方法,最后总结得到3种方法中IBI法的优势最大. 相似文献
53.
An important step towards the successful integration of information and communication technology (ICT) in schools is to facilitate their capacity to develop a school‐based ICT policy resulting in an ICT policy plan. Such a plan can be defined as a school document containing strategic and operational elements concerning the integration of ICT in education. To write such a plan in an efficient way is challenging for schools. Therefore, an online tool [Planning for ICT in Schools (pICTos)] has been developed to guide schools in this process. A multiple case study research project was conducted with three Flemish primary schools to explore the process of developing a school‐based ICT policy plan and the supportive role of pICTos within this process. Data from multiple sources (i.e. interviews with school leaders and ICT coordinators, school policy documents analysis and a teacher questionnaire) were collected and analysed. The results indicate that schools shape their ICT policy based on specific school data collected and presented by the pICTos environment. School teams learned about the actual and future place of ICT in teaching and learning. Consequently, different policy decisions were made according to each school's vision on ‘good’ education and ICT integration. 相似文献
54.
I. Werbrouck M. Antrop V. Van Eetvelde C. Stal Ph. De Maeyer M. Bats J. Bourgeois M. Court-Picon Ph. Crombé J. De Reu Ph. De Smedt P.A. Finke M. Van Meirvenne J. Verniers A. Zwertvaegher 《Expert systems with applications》2011,38(7):8178-8185
This paper discusses the generation of a high precision DEM (Digital Elevation Model) based on high density airborne LiDAR (Light Detection and Ranging) data for an interdisciplinary landscape archaeological study concerning the settlement history and environment in Sandy Flanders, a region to the north of Ghent (Belgium). The objective was to create a detailed topographical surface free of artificial features and topographical artefacts, in the form of a DEM, visualizing the natural and current topography through the implementation of true ground points only. The semi-automatical removal of these features and artefacts was based on topographical vector data, visual interpretations and slope analysis. Ultimately two DEM’s were constructed (1) a TIN (Triangulated Irregular Network) model, whereby the inherent large file format restricts the usability to large scale and (2) a grid model which can be used for small-, medium- and large-scale applications. Both datasets were used as an image that is interpreted using ancillary data from historical sources. Its usefulness is illustrated in a case of field pattern and microfield topography. Starting from this DEM, the approach of this landscape historical study is mainly retrogressive, i.e. starting from the landscape structures and elements that are still present in the contemporary landscape and moving into the past. 相似文献
55.
Proteomics has long been thought to hold the promise of producing results of clinical utility which will influence patient treatment and outcomes. A recent Wellcome Trust/EBI meeting and retreat--“Perspectives in Clinical Proteomics”--brought together experts from a broad range of stakeholder groups with an interest in ensuring proteomics achieves this aim. This viewpoint presents views derived from these forums, proposing a pathway for the development of next-generation proteomic analyses in the clinical setting from selection of candidates through to their validation and ultimate demonstration of utility through health technology assessments. Although not meant to be all encompassing, important elements for proteomics researchers to consider are presented. 相似文献
56.
Van Thanh Dau Thien Xuan Dinh Tanaka Katsuhiko Sugiyama Susumu 《Microsystem Technologies》2009,15(7):1039-1044
A gas-jet micro pump with novel cross-junction channel has been designed and fabricated using a Si micromachining process.
The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT) diaphragm actuator and fluidic network.
The design of the valveless pump focuses on a cross-junction formed by the neck of the pump chamber and one outlet and two
opposite inlet channels. The structure of cross-junction allows differences in fluidic resistance and fluidic momentum inside
the channels during each PZT diaphragm vibration cycle, which leads to the gas flow being rectified without valves. The flow
channels were easily fabricated by using silicon etching process. To investigate the effects of the structure of the cross-junction
on the gas flow rate, two types of pump with different cross-junction were studied. The design and simulation were done using
ANSYS-Fluent software. The simulations and experimental data revealed that the step-nozzle structure is much more advantageous
than the planar structure. A flow rate of 5.2 ml/min was obtained for the pump with step structure when the pump was driven
at its resonant frequency of 7.9 kHz by a sinusoidal voltage of 50 Vp–p. 相似文献
57.
58.
Flerackers C. Earnshaw R. Vansichem G. Van Reeth F. Alsema F. 《Computer Graphics and Applications, IEEE》2001,21(1):56-60
By exploiting a networked virtual environment architecture, we produced the gaming part of an interactive television drama series, TypoToons. For decades TV show makers have been inventing tools and tricks to enhance the stories they tell. Equivalents of, and additions to these conventional tricks in interactive media can only mature an interactive television if multidisciplinary teams can obtain hands on experience of these newly emerging worlds. The production team for TypoToons and the interactively participating audience provided an excellent opportunity to develop such a team 相似文献
59.
Van Gestel T. Suykens J.A.K. Van Dooren P. De Moor B. 《Automatic Control, IEEE Transactions on》2001,46(9):1416-1420
In subspace identification methods, the system matrices are usually estimated by least squares, based on estimated Kalman filter state sequences and the observed inputs and outputs. For a finite number of data points, the estimated system matrix is not guaranteed to be stable, even when the true linear system is known to be stable. In this paper, stability is imposed by using regularization. The regularization term used here is the trace of a matrix which involves the dynamical system matrix and a positive (semi) definite weighting matrix. The amount of regularization can be determined from a generalized eigenvalue problem. The data augmentation method of Chui and Maciejowski (1996) is obtained by using specific choices for the weighting matrix in the regularization term 相似文献
60.